Implementation of boundary conditions for optimized high-order compact schemes

The optimized high-order compact (OHOC) finite difference schemes, proposed as central schemes are used for aeroacoustic computations on interior nodes. On near-boundary nodes, accurate noncentral or one-sided compact schemes are formulated and developed in this paper for general computations in domains with non-periodic boundaries. The near-boundary non-central compact schemes are optimized in the wavenumber domain by using Fourier error analysis. Analytic optimization methods are devised to minimize the dispersion and dissipation errors, and to obtain maximum resolution characteristics of the near-boundary compact schemes. With the accurate near-boundary schemes, the feasibility of implementing physical boundary conditions far the OHOC schemes are investigated to provide high-quality wave solutions. Characteristics-based boundary conditions and the free-field impedance conditions are used as the physical boundary conditions for direct computations of linear and nonlinear wave propagation and radiation. It is shown that the OHOC schemes present accurate wave solutions by using the optimized near-boundary compact schemes and the physical boundary conditions.